Original subtitles

[Man Narrating] This is the epic story of our World.

But it's not the one We 're used to.

It's the story of how we almost didn't happen.

We turn back time 4. 5 billion years...

to our solar system still forming around the sun.

This planet is early Earth.

It's at a critical distance from the sun.

It is in this zone that liquid Water Will be able to exist.

Any closer and our future cities Would burn and our oceans boil.

Any further out and our future freezes over.

Earth's location is just one of many lucky breaks.

The next comes in the form of cosmic disaster.

A massive object the size of Mars collides into early Earth.

If the collision Were head-on, our planet Would have shattered.

Instead, the debris forms our moon.

The moon is a counterbalance, stabilizing Earth's rotation...

Which will prevent catastrophic swings in climate.

Another lucky break.

As Earth cools, the heaviest metals sink and form a spinning core...

sending a giant invisible force field around the planet.

A magnetic field that Will one day...

protect us from deadly radiation...

and keep our atmosphere from blowing away.

But since most heavy metals sank to the core...

Earth's surface is devoid of the vital materials-

the iron, tin, lead and gold-

that We Will one day need.

That is until Jupiter and Saturn step in to help.

Millions of miles away...

these massive planets shift in their orbits...

sending billions of metal-rich asteroids through space...

showering Earth...

and replenishing our supply.

Then another lucky break.

Jupiter's orbit stabilizes...

and its massive gravity begins to vacuum up most of the remaining rocks...

keeping our future home safe.

Without a giant neighbor like Jupiter...

Earth Would still be under constant asteroid attack.

If just a single one of these things had not happened in precisely the right Way...

our story Would unfold differently...

or not begin at all.

Earth Would not have the minerals and metals...

the stability...

the seasons...

to support the amazing saga that is to come.

In this special presentation, We 'Il see that everything is connected.

You can't look at this as tiny, little, remote events.

That these are huge, coupled aspects- events-

that themselves are part of a larger history.

They are big history.

[Narrator] We think of history as a timeline...

a series of events stretching a few thousand years into the past.

It's time to think bigger.

Instead of a line, imagine a Web of infinite connections...

interacting over billions of years...

linked together to create everything We've ever known-

our universe...

our planet and us.

History as We know it is about to get big.

[ Man ] Big history takes events all over the cosmos, all over the solar system...

all over our planet, and connects them together into a seamless whole.

And then connects those events in human history...

into the context of the planet, the solar system and the universe.

[Narrator] The story we just saw-

the series of lucky breaks that led to the formation of the Earth-

is What big history calls a threshold moment.

[ Man ] The idea is basically that the early universe, in all sorts of ways...

was really quite simple.

No stars, no life, no planets.

And then gradually, over 13 billion years, new things appear.

And that idea provides a great shape and structure...

and a sort of plot line.

We focus on a number of moments when something critical appeared...

and that's what we mean by threshold moments.

[Narrator] In the story of big history...

there are a total of eight threshold moments.

Moments When the universe crosses a line...

and can never turn back.

The creation of the Earth is the fourth threshold.

We 'Il re veal them all...

and uncover the surprising secret that links them together.

But to do that, We have to go back to the beginning-

the first threshold moment...

nearly 14 billion years ago.

A moment that had only a split second to unfold precisely as it did...

or the entire universe might have ended shortly after it began.

It is the quietest quiet there has ever been.

And then suddenly, out of nothing, everything begins.

[ Explosion ]

It is big history's first threshold.

The big bang.

In a fraction of a second, all the energy that Will ever exist...

appears in an inconceivable flash.

[ Benjamin ] Everything begins, as far as we know, at this moment...

and from the moment it appears...

physicists can offer a very coherent account of everything that happens since.

[Narrator] Before the first second has passed...

the fundamental forces appear that will go vern all existence forever.

One is the gravity that holds us to the Earth...

and that We Will need to overcome in order to fly.

Another- the electromagnetism that lets you make a cellphone call.

[ Beeping ]

The big bang is the creation event that lays the ground rules.

It lays the ground rules of the fundamental forces-

the strength of gravity, the speed of light...

all of the things that Will shape the rest of the history of the universe.

[Narrator]And in these first few seconds, a lot could have gone Wrong.

If gravity had been just a tiny bit stronger...

all of existence Would have collapsed in on itself.

A bit Weaker...

and stars Would never be able to form.

But the big bang occurred at just the right force...

to set our entire history in motion.

Which is Why it's the first of eight thresholds.

We Will see that they are all mysteriously connected.

Eight thresholds that explain everything.

Eight portals that lead to us-

[ Heart Beating ]

including the next one...

the moment When the immense heat, darkness and chaos of the early universe...

suddenly explodes into a trillion trillion points of light.

[Narrator] Big history has begun to reveal...

the eight biggest turning points in the story of our universe.

Eight threshold moments...

that Will mysteriously lead to us.

[ Heart Beating ]

The first-

the big bang-

[ Explosion ]

exploding in just the right Way to create forces like gravity.

But it's still too hot to form atoms.

All that is about to change.

We are about to reveal the second threshold moment.

[ Markley ] Only at the point of about 380,000 years...

have things cooled enough that we can finally get matter as we recognize it.

Without a cooling universe, there's no way that we or anything else...

that has real structure would exist.

[Narrator] The first atoms to appear are hydrogen and helium...

the two most basic elements.

But their formation is not the second threshold.

Hydrogen and helium are just the building blocks of the portal yet to come.

Since all matter exerts a gravitational pull...

giant clouds of these atoms begin to clump together...

into forms We recognize today.

[ Filippenko ] Gravity is the sculptor of the universe.

And small variations in the density of the universe at early times...

led to the formation of these gigantic structures-

galaxies and clusters of galaxies and super clusters of galaxies...

separated by enormous voids.

This is mega engineering on the largest scales.

[Narrator] NoW, Within these mega structures...

trillions of smaller clouds of hydrogen and helium begin to condense and spin.

So gravity is working on these clouds- crushing, condensing, compressing.

Inside them, temperatures are increasing, pressure is heating up.

And eventually, once a certain temperature is reached inside these vast clouds-

roughly 10 million degrees Celsius- nuclear fusion will take place.

[Narrator] Once these conditions are met...

and the critical amount of atoms, temperature and pressure come together...

We reach another turning point- big history's second great threshold.

Stars light up.

[ Markley ] There was no light immediately before this...

because there was nothing in the universe to create light.

And we hit a very significant threshold in the history of the universe.

"Let there be light."

[Narrator] From this point onward...

the universe crosses through a portal from Which there Will be no turning back.

Before stars, all the energy in the universe emanated from one source-

the big bang.

NoW there are sites scattered throughout the universe...

hot spots of energy, Warmth, density.

The first generation of stars light up the universe.

But their fuel begins to run low.

They start to burn out.

It is With the death of this first generation of stars-

- [ Explosions ] - that We cross another portal in our epic story.

Big history's third great threshold-

the creation of complex elements.

Within the dying cores of stars...

simple elements fuse into larger and more complex atoms.

For the first time, hydrogen and helium create brand-new elements...

that Will make the modern universe possible.

[ Benjamin ] As stars begin to run out of hydrogen...

they heat to higher and higher temperatures.

They start converting helium to more complex elements...

and this whole process continues right up the periodic table.

[Narrator]As it dies, each star becomes an element factory...

creating just the right conditions to form the elements.

And once they're formed, the universe Will never be the same.

A star uses the ashes of one set of nuclear reactions...

as the fuel for the next set.

Hydrogen to helium, helium to carbon and oxygen...

carbon and oxygen to neon and magnesium, then silicon and sulfur...

and then iron.

[Narrator] So more than 12 billion years ago...

stars are creating the element...

that Will make possible everything from the Iron Age to the ironclads.

[ Explosion ]

But these dying stars don't have enough energy to create anything heavier than iron...

until they explode as supernovas-

[ Explosion ]

the biggest blasts since the big bang.

The intense heat and pressure produces elements heavier than iron.

But even these mega blasts are not enough to create the heaviest elements...

like the gold that Will draw Europeans across the Atlantic...

and cause millions to flood into California.

For that, you need the biggest blast of all-

the collision between the ruins of two supernovas...

known as neutron stars.

These new elements billow out into space, forming new clouds...

that come together in new, second-generation stars.

Each time the process repeats, more elements are created.

[ Markley ] As you head further up that periodic table...

you are basically seeing the order of creation and the difficulty of creation...

and how much energy is required to create them.

[ Explosion ]

[Narrator] Some elements Will be abundant, others rare.

Their proportions Will have profound effects on all of history to come.

For example, there is more silver in the universe than there is gold...

because it requires more energy...

and is more rare to get those events where gold can be created.

[Narrator] But that is all Waiting for a distant future.

It Will take eons before dying stars create enough of the raw materials...

like iron, nickel and calcium to form rocky planets like Earth.

So during the first few generations of stars, Earth-like planets can't exist...

and neither can life.

But billions of years after the big bang, a newer generation of stars appears...

including our sun.

This time there are enough new minerals and metals to create rocky planets as Well.

[ Markley ] It is truly mind-blowing when you realize...

that the elements that are present on our Earth and in our sun...

cannot exist unless there has been at least two generations of star systems before us...

that have lived and died.

Can you imagine? The elements in our body...

have to have been through this event twice before...

before you can get a creature like us.

[Narrator] Early thresholds reveal that the first atoms in the universe...

are reincarnated throughout billions of years...

from one element to another.

From star to exploding star.

From isolated early atoms...

to the elements that form everything around us.

Some of the atoms in our bodies are more than 13 billion years old.

These are the building blocks that will lead us to the next threshold...

and the most mysterious turning point in the big history of the universe-

the one that Will finally lead to us.

[Narrator] Big history is a new story of mankind...

that traces our origins through eight pivotal moments.

The first three- the big bang, the birth of stars...

the creation of complex elements-

transform everything in the universe...

and lead us to the fourth monumental turning point in our big history-

the formation of Earth.

This is our galaxy more than four and a half billion years ago.

An ancient star collapses and explodes-

[ Explosion ]

launching a massive shock Wave into a nearby cloud of gas and dust.

Its force causes the cloud to spin.

Gravity crushes and compresses it...

sculpting the cloud and heating it up to 10, 000 degrees.

And from the remains of an ancient star...

a new one bursts into light.

Our sun illuminates eight young planets forming around it.

As we've seen, a series of improbable events noW line up...

to push us across the fourth threshold...

like pieces of a grand and infinite puzzle leading to an Earth capable of sustaining life.

First, a massive collision.

[ Explosion ]

It created a huge molten disk of rock around the Earth...

which rapidly, um, coalesced to form the moon.

[Narrator] By a stroke of luck, our moon is one of the largest in the solar system...

so its gravity is powerful enough to affect how the Earth behaves...

giving us a steady climate and predictable seasons.

If it hadn't been for the presence of the moon...

Earth's axis of rotation would undergo...

chaotic, giant changes in tilt.

And this would lead to huge disruptions in climate.

And it's unlikely that advanced, complex creatures such as ourselves could have evolved.

[Narrator] But even With the stability created by the moon...

this young planet isn't ready to become a home.

Big history can't move to the next threshold Without Water.

And most of it was just blown away by the heat of the moon-forming impact.

But the chaotic early solar system comes to the rescue.

[ Filippenko ] Meteoroids and asteroids rich in water...

come from the outer parts of the asteroid belt...

and are thought to have brought a lot of the water to the Earth.

[ Christian ] You turn on a tap, and you may well be drinking stuff...

that was delivered to you personally by an asteroid...

about four and a half billion years ago.

[Narrator] And noW deep in the ocean Waters...

carried to Earth by comets and asteroids...

We are about to Witness the fifth and most mysterious of the big history thresholds.

Life.

How exactly does life emerge?

It's one of our most profound questions.

Some believe that life may have crash-landed on Earth in meteors or comets.

But most believe that life on Earth starts With a chemical reaction...

down in the deepest depths of the ocean...

Where heat rising from the planet's molten core tears apart the seafloor.

Superheated gas and lava vent through the cracks...

and ignite a revolution.

In this broiling soup, a new kind of chemistry emerges...

a biological blueprint for every living thing that Will ever exist-

a secret code called D. N.A.

Just four chemicals Will combine in millions of Ways...

to instruct every cell on how to do everything...

beginning With bacteria...

the simplest and oldest form of life.

[ Benjamin ] Here's where early forms of bacteria appeared...

feeding off the energy and the heat that was coming out of these volcanic eruptions.

Here, we think, the first life on Earth appeared...

beside these great undersea mountain ranges.

[Narrator] Life is the only thing in the universe that can store and pass along information...

reproduce itself and evolve.

But how does a simple microscopic organism...

evolve into something as complex as a human?

The path from bacteria to man is a mysterious series of transformations...

With an infinite number of possible outcomes...

but only one that leads to us.

The seeds of everything that Will happen on the future Earth...

are all descended from these simple beginnings.

Earth- 542 million years ago...

three billion years after life first appears.

In a geological instant, the seas explode With complex plants and animals.

All the basic body types that Will ever exist-

heads, mouths, eyes...

fins that Will evolve into limbs...

jaws and teeth-

all of them suddenly appear.

475 million years ago, plants begin to spread across the land...

transforming the Earth into a World of lush forests...

With abundant food and shelter.

[ Birds Chirping ]

Some plants evolve into trees that, along With metals brought by meteors...

Will become key building blocks of civilization.

To escape the carnage in the seas...

some creatures crawl onto land as Well.

At first they're forced to return to the salty seas to reproduce.

But then they discover a Way to bring a bit of the ocean With them.

The egg.

[ Man ] When we started crawling onto the land...

certain creatures figured out- birds, reptiles- that they could lay eggs...

that have a nice hard shell that kind of keeps the salt water contained...

in a small space for them.

[Narrator] The egg is a critical development.

It allows animals to move permanently onto land-

animals that Will continue to evolve and grow more complex.

But noW big history reveals a fundamental secret that governs all life on the planet.

The more complex you are, the more fragile you become.

Some simple bacteria can survive being frozen...

boiled, crushed or dried out.

Complicated animals like us cannot.

So When the Earth is shaken by a drastic change in climate...

or volcanoes poison the air...

or a giant meteor strikes...

life faces the ultimate threat-

extinction.

Five times since complex animals appear...

more than 50 percent of all life is Wiped away.

But these catastrophes clean the slate for new creatures to evolve and fill the void.

Without them, big history's future thresholds could never occur.

A good way to put it is that every extinction does reshuffle the deck.

You just take all of the playing cards, put 'em back, mix it up...

and deal yourself a new hand.

[ Squeaking ]

[Narrator] One catastrophic reshuffling...

ends the 165-million-year reign of the dinosaurs...

When a huge asteroid plunges into Earth 65 million years ago.

Temperatures plunge, plants don't grow.

[Narrator]A great era in Earth's history has come to a fiery end-

[ Chittering ]

clearing the Way for the age of mammals.

The age of us.

But What most people don't know...

is that it almost...

didn't happen.

[Narrator] Big history reveals how a series of rare and unlikely connections...

across three billion years...

make Earth a thriving planet.

But What does it take for the planet to make us?

And What exactly does it mean to be human?

It all starts With a lucky break that kills the dinosaurs-

[ Explosion ]

and clears the Way for the ultimate rise of mankind.

[ Chittering ]

With the dinosaurs gone, tiny mammals begin to take their place.

[ Benjamin ] Humans are ultimately evolved, descended from these mammals.

If there had been no asteroid collision 65 million years ago...

would the human species even exist?

Probably not.

[Narrator] But as we've seen With so much big history...

things could have been very different.

[ Christian ] If that asteroid would have been on a trajectory...

five minutes earlier or five minutes later, it would have missed the Earth...

and the dinosaurs would probably still rule the Earth.

- [ Roaring ] - [ Screeching ]

[Narrator] Instead, life begins a new chapter.

Fifty million years ago, the spread of a new plant-

grass- draws mammals out of the forest.

Over the next 45 million years...

the ancestors of horses grow larger, stronger and faster.

[ Whinnies ]

Sheep, goats and aurochs-

the ancestors of cows- evolve.

[ Bellows ]

Mankind Will use them for food and power...

to build civilizations.

But first, on the savannas of Africa, more than four million years ago...

some primates take the first steps toward becoming human.

[ Valle ] We left the trees, and the grass was really tall.

We had to see over it.

And walking on our hind feet allowed us to hold babies and tools...

and hunt and free up our hands and our opposable thumbs.

[Narrator] Since We no longer need to Walk using our knuckles, or swing from trees...

our shoulders and Wrists evolve to do something unique in nature-

throw accurately-

making it easier to hunt and kill for meat.

[ Markley ] Look at the natural world. How do you kill something?

Almost always you kill something by getting up close and personal.

You do it with your claws. You do it with your teeth.

Now look at your claws. Look at your teeth.

Do you really want to get up close and personal and try to kill something...

with these pathetic teeth, these pathetic claws?

- I don't think so. - [ Shouting ]

[Narrator] This change in our arms leads to an arms race...

that Will define human history.

[ Man ] We can cause death at a distance...

in ways that no other species can.

[Narrator] There are thousands of species on Earth that eat meat...

but only one that cooks it.

Early man uses fire and tools to make meat easier to digest...

a behavior that changes our biology.

If you eat meat, you get highly concentrated energy...

but it's hard to digest and chew.

Now if you cook it, that's like predigesting it.

That would mean that the gut can get smaller.

If the gut gets smaller, there's energy available for another organ to grow...

such as the brain.

So this may be a very neat explanation for the very rapid growth in brains.

[Narrator] The human brain is not the largest on Earth...

but pound for pound, it's the most powerful...

able to process one quadrillion pieces of information in a lifetime-

more than any other living creature.

[ Bird Calls ]

So life on the African savanna transforms our bodies and our brains...

and its legacy is still imprinted in our minds.

In need of Water, We constantly search...

for the shiny sparkle of sunlight on rivers and streams...

one reason Why today We are attracted to shiny substances like gold.

After 350, 000 years of evolution in Africa...

our ancestors have separated themselves from every other species on Earth.

We have crossed a threshold that makes us uniquely human.

But What is it? What sets us apart?

It's the key that unlocks the sixth big history threshold...

and it begins When one person makes a disco very-

like a new Way to kindle fire or a new kind of tool-

and shares it With his clan.

The idea spreads through the population, then across generations.

Humans begin to build a database of knowledge...

built on millennia of shared experience.

What starts With changes like cooking meat and growing larger brains...

propels us across the next great threshold in big history...

a threshold as important for humanity...

as the formation of Earth...

or the birth of life.

Big history calls it collective learning.

[ Christian ] Here now we have the first species in the history of our planet...

in which information can accumulate from generation to generation.

And that, I think, tells us everything about what makes humans different.

[Narrator] 60, 000 years ago.

The planet has molded our ancestors into modern humans...

With brains and skeletons identical to our own.

Collective learning has given us the tools and skills We need to dominate the planet.

But despite all our advances, the human story could have ended here...

isolated in Africa.

Species that are confined to only one continent can easily go extinct.

But big history reveals how the Earth shifts in a Way that Will spread man...

and all the things he's learning, all around the planet.

The Ice Age lowers the sea level between Africa and Arabia...

creating a gateway to an otherwise unpopulated World.

A tiny group, perhaps just a few hundred...

get on a handful of rafts and cross these narrow straits.

This African exodus only happens once.

In the future, all humans outside Africa Will be descended from this one tiny clan.

In these new lands, the Ice Age Will test the limits of collective human learning.

Faced With extreme cold, people innovate.

They cover themselves in a new invention-

head-to-toe clothes...

tailored With needles and thread.

Their dark skin gets almost no direct sunlight...

Which is critical in creating vitamin D.

[ Shea ] One way of dealing with that was to evolve lighter skin...

that didn't block the rays of the sun as much.

[Narrator] This change begins to create the fundamental divisions We think of today...

as race.

Instead of being slowed by the Ice Age, humans adapt and spread.

One group makes it to Siberia and crosses a bridge of land to North America.

10, 000 B. C., glaciers start to melt.

Seas rise.

The bridge to Siberia is submerged.

The Americas are cut off.

Suddenly, water enters the Bering Straits...

so populations now get sort of locked in to the regions they've migrated to.

[Narrator] From noW on, for thousands of years...

it Will be as if humanity lives on different planets.

But that separation Will ultimately prove our similarities...

as humans everywhere do remarkably similar things-

launch empires, build pyramids...

master new technologies, cross new thresholds...

and begin big history's fateful march to the modern World.

[Narrator] Big history reveals...

how collective learning- threshold number six in big history-

gives man the tools We need to survive the Ice Age.

NoW as the glaciers retreat...

the very success that allows humanity to spread to the farthest reaches of the planet...

might also be our downfall.

There's too many people on planet Earth and not enough food.

The solution is the seventh threshold of big history.

It might be hard to imagine how it fits in With such epic events as the big bang-

[ Explosion ]

and the origins of life...

but for mankind, it Will change everything...

a true turning point that revolutionizes how We live.

For the first time, We stop moving...

and settle down.

It's a step toward building the civilizations that Will dominate the entire planet.

Threshold number seven.

The farming revolution.

This is arguably the most important revolution in all of human history...

perhaps even in the history of our planet.

[Narrator] Beginning 10, 000 years ago...

the changeover from hunting and gathering food to farming...

is a triumph of collective learning.

We seize control of evolution by breeding wild grasses into our most important foods...

like corn, Wheat...

barley and rice.

[ Christian ] Of course, they didn't understand about genes...

they didn't understand the science of what they were doing...

but once humans start really concentrating on a particular species...

and looking after it, then you can find very quickly, within just a few generations...

the species itself starts changing.

[Narrator] The natural World becomes our laboratory.

Wild beasts are no longer just enemies to be feared or hunted.

They are creatures to be tamed and bred, turned into vital allies.

We domesticate Wild Wolves into dogs...

Wild pheasants into chickens...

Wild boars into pigs...

the fierce aurochs into the modern cow.

[ Lows ]

All modern cows- more than one billion animals, 250 different breeds...

providing all of the 130 billion pounds of beef that we eat every year-

descend from a herd of just 80 aurochs...

that our ancestors domesticate 10, 000 years ago.

[ Bellows ]

This revolution also gives us our most powerful animal ally-

the horse-

[Horse Whinnies]

Which today has a huge and surprising impact on how We speak.

The horse is first tamed by Asian tribes...

that speak an ancient language called Proto-Indo-European.

[ Nickers ]

With this radical new Way of getting around...

they fan out, spreading their language far and Wide.

Over time, it branches into hundreds of languages...

spoken by almost half the World.

[ Benjamin ] We wouldn't be having this conversation- at least not in English-

if it was not for the role of the horse in spreading language, culture and humans.

[Narrator] The farming revolution also depends on chemistry...

and the superpower of salt.

To survive as a farmer, the food you harvest in the fall has to last all year.

Salt pulls moisture out of food, Which kills off microbes...

and keeps it from rotting.

One of the great problems for agricultural societies...

is how to preserve things, and salt is the answer.

[Narrator] Preservation turns farming from a lifestyle change...

into a revolution.

For thousands of years, the only jobs that existed...

involved hunting or gathering food.

NoW, With the ability to store food and build up a stockpile for the future...

for the first time in history, people can devote their energy...

to something more than survival.

It is the beginning of mankind’s first job market.

[ Christian ] You start getting a division of labor.

Some people specialize as soldiers...

some as priests, some as, uh, metalworkers...

and eventually some as rulers.

[Narrator]And What makes the farming revolution even more momentous...

is that by planting seeds, We begin to put down roots...

causing much more than just food to grow.

Villages become towns...

towns become cities...

and cities become civilizations...

ushering in an age of all-powerful rulers.

One of those rulers, an Akkadian king called Sargon the Great...

raises a huge army, conquers his neighbors...

and creates something entirely new-

Where one king rules over many different cities and peoples.

It is the World's first empire.

It's a pattern We see across the ancient World.

Where cities rise, empires follow.

[ Benjamin ] This impetus to construct empires appears to get deeply embedded...

in the cultural D.N.A. of all these civilizations.

[Narrator] Empires depend on loyalty from thousands of subjects over vast territories.

So early rulers build giant mega structures to signal their awe-inspiring power.

Thousands of common laborers pile giant stones...

into enormous artificial mountains-

ancient pyramids that rise around the World...

a pattern that links human civilizations across the globe.

As civilizations grow and connect...

our Wealth of collective learning expands...

and We soon need a Way to record and share knowledge.

[ Shea ] All of the world's major civilizations at some point confronted...

the problem of there being too much information to keep it in your head...

that they had to develop permanent ways of recording information.

[Narrator] So We begin making marks on clay, stone, papyrus and bamboo...

to help us remember things.

Writing is a breakthrough that allows us to pass on our experiences...

directly to future generations.

From Writing to pyramids...

to the rise of the modern metropolis.

Everything We call civilization...

can trace its origins back to the farming revolution...

a big history threshold that transforms the Way We live.

But although common human traits unite us...

the natural World of climate and geography Will divide us...

and plunge the World into an epic clash...

that threatens to bring entire civilizations crashing down.

[Narrator] Big history is an epic new Way to look at the World...

connecting the traditional history of empires and civilizations...

to the geology of mountain ranges...

the evolution of animals...

even the Earth's tilt and climate.

Cities and civilizations take hold in Warmer climates...

places Where it's easier to grow food.

In the north, Where it's too cold for most crops...

grass is one of the few plants that can survive.

Herd animals thrive on it, so people here saddle up instead of settling down...

and become expert herders and raiders.

[ Markley ] Horse-based warrior cultures...

are going to be the optimal mode of existence.

[Narrator] So climate divides the Old World...

and gives us different destinies.

Where it's Warm- permanent, prosperous settlements built on farming.

Where it's colder- roving bands of nomads...

Who sometimes loot and pillage riches from the south...

and even bring entire civilizations crashing down.

From the tribes that swarm over China's Great Wall...

to the Huns, Goths and Vandals Who destroy the Roman Empire...

to the Mongols Who conquer most of the known World...

it's an epic conflict that lasts 5, 000 years.

But climate is not the only force With a profound impact on big history.

Geology-

the shape and movement of continents...

and the location of formidable mountain barriers...

plays a vital role.

In Europe and Asia, civilizations grow faster and more massively...

than their counterparts in the Americas.

So What does the Old World have that the New World doesn't?

The Earth reveals that in the eastern hemisphere...

plate tectonics aligns the land from east to West...

and a single mountain system, the Alpide Belt, stretches across two continents...

from the Alps to the Himalayas and beyond.

Because the Old World and its mountains are oriented from east to West...

people can migrate easily alongside them for thousands of miles...

bringing their crops, animals and ideas.

[ Markley ] Human migration tends to run east-west...

because the length of the days remains the same...

the temperature tends to remain about the same...

the rainfall tends to be pretty consistent.

That means that whatever you were growing in one place will probably transfer.

[Narrator] Here, the busiest land trade routes in history...

carry new technology from one place to another...

connecting everyone in a vast Web that enriches civilizations...

from China to Europe.

On the other side of the World...

the American continents are oriented in a north-south direction...

so crops grown in North America...

rarely survive in the different climates of the south.

And North America's great mountain systems-

the Appalachians in the east...

and the Rockies and Sierras in the West-

split the continent With north-south barriers that obstruct migration and trade.

By looking to geology...

big history reveals Why it's harder for civilizations in the Americas to exchange ideas.

But there's another obstacle that sets the New World apart from the old.

There are no large animals to domesticate for food or transportation.

A small thing like the lack of horses can have a big impact on civilization.

[ Christian ] Most transportation is still by human porters.

That may have limited the possibilities...

for commerce, trade and exchange in those areas.

[ Man ] On a horse, you can get from point "A" to point "B"-

and they're a hundred miles apart- relatively easily.

That's not a huge deal.

For people, you know, running, that's a very, very big deal.

[Narrator] So by connecting traditional history to science...

big history reveals Why New World empires lagged behind those across the Atlantic...

in size and technology.

The Old World alignment of continents and mountains...

and access to animals like horses and camels...

create conditions that are just right.

They link us across thousands of miles...

like synapses in a vast interconnected brain of human knowledge...

amplifying the uniquely human skill of accumulating and sharing information-

the big history threshold called collective learning.

So an idea that starts in one small part of the globe...

has the chance to change the World.

Some new ideas can be explosive.

850 A. D.

The Chinese unlock the chemistry of Gunpowder...

[ Explosion ]

and it spreads across the continent all the Way to Europe in just 300 years.

And in 1450, When a German blacksmith named Johannes Gutenberg...

develops a radically improved method of mechanical printing...

it becomes the greatest boost to collective learning...

since the invention of Writing 5, 000 years before.

[ Christian ] Printing encouraged mass education.

Mass education encouraged more exchanges of ideas...

and made the development of new technological innovations...

perhaps slightly easier in Europe than in other parts of the world.

[Narrator] Technology tears down barriers.

So after millennia of discovery and invention...

We 're finally ready to conquer Earth's greatest divide-

the oceans.

For 15, 000 years, the oceans separate humanity into isolated zones-

the Americas...

Africa and Eurasia...

Australia-

Where We develop in different Worlds, each unaware of the others.

But technology ushers in a new age Where nature's most formidable barrier...

becomes a highway.

Europeans cross the Atlantic for the first time...

equipped With a series of big history's lucky breaks.

They Will dominate the Americas using horses...

guns...

and a terrible secret Weapon-

disease.

The Europeans bring microbes to Which the Americans have no immunity.

Within a hundred years of Columbus, up to 90% of them Will die.

It's a definitive conquest.

But by mastering the ocean, European explorers unite the World.

Mankind trades new crops, animals and resources like gold and silver...

in an unprecedented global exchange.

[ Christian ] The last time in the planet's history...

when there was a biological exchange over the whole globe...

was 250 million years ago...

when all the continents were gathered together in Pangaea.

But this time it's caused not by geology but by human beings.

By one particular species that's moved goods all around the world.

[Narrator] Our epic story has taken us around the globe through seven thresholds.

But What is the eighth and final threshold in big history?

And What secret connects them all?

[ Heart Beating ]

[Narrator] By the year 1500...

mankind is breaking the ocean barrier.

And these new liquid highways amplify the very thing that makes man so special-

the sharing and spreading of knowledge.

What big historians call collective learning.

[ Christian ] I think globalization from 1500...

is a sort of gear shift in the speed of collective learning.

[Narrator] This is the first World Wide Web.

But the network is slow.

Information, ideas, inventions...

can only spread as fast as a horse can run...

or a ship can sail.

To circle the globe takes over a year.

But soon it all begins to change.

By revealing connections across space and time...

big history shows how mankind Will cross another portal...

thanks to a revolutionary machine.

To create this machine, big history connects metals brought by meteors...

ancient plants reincarnated as coal...

and the almost magical property of Water as it shape-shifts into a new form.

That revolutionary machine?

The steam engine.

[ Benjamin ] By heating water, you create this steam pressure.

It can force a piston, for example, to start moving up and down.

Machines to drive spinning machines that will create textiles much, much faster.

[ Train Whistle Blows ]

And then you can put it onto a platform with wheels...

and lay iron rails across the landscape.

All of this is a product of utilizing this extraordinary property of heated water again.

[Narrator] The steam engine leads to the gasoline engine...

and ignites a new threshold in big history-

the modern revolution.

[ Chattering ]

For all of history, We have been limited almost completely...

to power from human and animal muscles-

[ Camels Grumbling ]

Wind and flowing Water.

NoW mechanical engines...

fueled by the power of the sun captured in ancient plants...

make us far more productive and powerful.

By 1900, the World's steam engines Will equal the power of five billion men.

The modern revolution accelerates everything-

how We produce and grow things...

- how We travel and communicate. - [ Tapping Morse Code ]

And it elevates man to a unique status in the story of our planet.

[ Christian ] A single species for the first time in almost four billion years...

has become so powerful that it dominates the biosphere.

And that's a fantastically interesting period in history, and we're living in it right now.

[Narrator] It is an era unlike any before.

But power is not the only key to open this portal.

The other is information.

Iceberg straight ahead1 .

Throughout all previous history, We Were tethered to our voices...

Which could only travel as far as a sound Wave could carry them-

a maximum of600 feet.

But noW our voices and ideas can ride on radio Waves...

made possible by the electromagnetic force born in the big bang.

Today, there are seven billion cellphones in the World-

one for every person on Earth.

We are each connected to a global network...

that transmits information at the speed of light.

I mean, short of teleportation, I really can't think of anything more magical than that.

[Narrator] In our modern era, the pace of progress explodes...

leading to a staggering fact.

During the era of the steam engine...

it took 150 years for man's collective knowledge to double.

Today, it takes two years.

By2020, it Will take 72 hours.

Big history brings us from the big bang...

through a series of amazing thresholds...

to the World around us today.

But can it foresee mankind's next momentous turning points?

And do they promise even faster progress...

or the end of everything?

[Narrator] Big history tells the story of everything...

from the beginning of the universe...

to the World around us today...

in What big historians call threshold moments.

But What is the secret key, the fundamental mystery...

that links them all together?

To reveal that secret...

We first have to understand a basic law that governs everything in the universe.

The natural tendency of all things is to move from order...

to disorder.

From structure to disintegration.

From the complex to the simple.

An egg can break...

but its pieces can't form a new egg.

A newspaper can burn to ashes...

but the ashes can't become a newspaper.

Scientists call it the law of entropy.

Throughout all time and space, the universe has been ruled by this law.

But When We consider the nearly 14 billion years of big history...

We discover What appear to be rare and remarkable exceptions.

Moments When everything lines up in just the right Way...

and seems to defy this natural law of entropy.

To go from the massive explosion of the big bang...

to the structure of a star.

From the swirl of chemicals in ancient seas...

to a strand of living D. N.A.

From a simple universe to a complex World.

For big history, that is the secret hidden in the heart of every threshold...

a pattern that links us through all of time and space.

Eight moments When the universe seems to defy its most basic law...

and instead moves from the simple to the complex.

Eight moments when we move from chaos...

to order.

But a mystery remains.

How and Why in these instances...

did the universe seemingly defy its own law of chaos?

The answer lies in a cosmic force that emerged from the big bang-

gravity.

Because of gravity, our universe is not evenly distributed.

Instead, there are hubs, galaxies...

stars and solar systems...

divided by massive voids.

In those hubs, energy and matter converge.

Trillions of interactions occur...

and in a swarming hub, the improbable becomes possible.

[ Filippenko ] Gravity can form stars that form energy...

that bathes the planets surrounding them...

which gives rise to life...

and life itself then has all these interactions...

that lead to increasing complexity.

[ Christian ] Most of the universe is still very simple.

So things get complex only in particular pockets of the universe...

where we have the Goldilocks conditions where conditions are just perfect.

[Narrator] These hubs appear throughout space and time...

in stars that forge elements...

ancient seas that produce life...

and even in cities on Earth.

[ Filippenko ] Giant cities form with huge amounts of activity.

And then there are of course these great expanses and not much activity.

All these things come about as a result...

of just repeated interactions of particles obeying the laws of physics.

And there's just a few laws of physics.

[Narrator] So What is the next threshold?

Will life, complexity and thresholds go on forever?

Or does big history foresee new moments...

Where mankind, life itself...

even the entire universe...

come to an end?

[Narrator] Big history has revealed how a series of eight giant thresholds...

ultimately lead to the advanced civilization that surrounds us today.

But What thresholds lie in the future?

To be considered a threshold in big history, an event has to alter things fundamentally...

irreversibly changing our modern World.

So What thresholds lie ahead?

What Will the ninth be?

[ Rumbling ]

One possible candidate-

the point When humans begin to live on other planets like Mars.

Another possibility- the moment our own technology overtakes us.

Still, another possible threshold...

Would be discovering intelligent creatures from other planets...

or being discovered by them.

But we've also seen that threshold moments can occur in the aftermath of catastrophe.

Like a cosmic collision.

There are still sort of rogue asteroids wandering around our Earth.

[Narrator] Scientists calculate that an asteroid six miles Wide...

could Wipe out humanity...

just as a similar impact Wiped out the dinosaurs 65 million years ago.

- The explosion of a nearby star- - [ Explosion ]

could also cause a planet Wide cataclysm.

But disaster doesn't only come from space.

Here on Earth, the next threshold might follow a Worldwide natural disaster.

Like the dawn of a new Ice Age.

Or the toxic blast of a super-massive volcano.

And even a cataclysm of our own invention-

from thermonuclear War...

to environmental destruction.

[ Christian ] But on the other hand...

the story of human innovation...

is fantastically creative.

I mean, we are staggeringly creative.

We are so clever as a result of collective learning...

that if our species can't solve these problems...

I have no idea who can.

[Narrator] Big history is about looking at our World...

and our future in different Ways.

On an astronomical scale across billions of years...

our fate is much more clear.

Our story of moving from simplicity to complexity is only temporary.

Billions of years from noW, the sun Will expand and sterilize the Earth.

[ Benjamin ] All the seas will boil away...

and the sun will shrink and contract and then end up as a white dwarf...

and then a black dwarf- no energy, just this dead lifeless object floating in space.

[Narrator] Out in the universe already today...

90% of the material to make new stars has been used up...

so fewer Will be formed.

The story of the universe...

this series of thresholds that led to our World today...

Will begin to reverse.

Instead of becoming more complex, things Will become more simple.

Stars will stop forming. They will stop creating new elements.

[ Filippenko ] Eventually, if the universe expands forever...

it'll cool down to essentially absolute zero everywhere.

[Narrator] The story of big history Will come to an end...

in a darkened cosmos Where nothing Will be created.

[ Christian ] And in the far distant future...

the universe is going to be extraordinarily simple again...

and it will cease to be able to create complex things.

So that means something quite magical about the time we live in.

We live in the springtime of our universe.

That's a time when our universe was capable of creating beautiful things...

like hummingbirds or redwoods or you and me.

[ Heart Beating ]

[Narrator]And it's also the time When mankind undertakes a profound quest...

to understand the big picture...

to find our place in the grand continuum of time.

Our infinite link to the brilliant beginnings...

the quiet end...

and the transformative power of this mysterious universe.

The story We call big history.